
library(testthat)

source("user_code.R")
test_that("plot variable exists and is a ggplot object", {
  expect_true(exists("plot"), info = "The plot variable must be defined.")
  expect_true(ggplot2::is.ggplot(plot), info = "plot must be a ggplot object.")
})

test_that("plot uses correct data and mappings", {
  mapping <- plot$mapping
  expect_true("x" %in% names(mapping) && rlang::as_label(mapping$x) == "horsepower", info = "x-axis must be mapped to horsepower.")
  expect_true("y" %in% names(mapping) && rlang::as_label(mapping$y) == "mpg", info = "y-axis must be mapped to mpg.")
  expect_true("colour" %in% names(mapping) && rlang::as_label(mapping$colour) == "type", info = "color must be mapped to type.")
})

test_that("plot includes professional theme", {
  th <- plot$theme

  # theme_minimal removes panel background and border
  expect_true(
    inherits(th$panel.background, "element_blank"),
    info = "panel.background should be blank (professional theme expected)."
  )

  expect_true(
    inherits(th$panel.border, "element_blank") || is.null(th$panel.border),
    info = "panel.border should be blank or NULL (professional theme expected)."
  )
})

test_that("plot includes custom title and axis labels", {
  labs_list <- plot$labels
  expect_true(!is.null(labs_list$title) && nzchar(labs_list$title), info = "Plot must have a custom title.")
  expect_true(!is.null(labs_list$x) && nzchar(labs_list$x), info = "Plot must have a custom x-axis label.")
  expect_true(!is.null(labs_list$y) && nzchar(labs_list$y), info = "Plot must have a custom y-axis label.")
})

test_main.R

Master the essentials of data visualization and reporting in R. Learn to create compelling graphics, perform exploratory data analysis, and communicate insights effectively using R's powerful tools.

Learn the basics of data visualization in R, focusing on the ggplot2 package and its core plotting capabilities.

Dive into EDA techniques in R, including summary statistics, visual inspection, and outlier detection.

Learn how to turn your visualizations and analyses into clear, actionable reports.

Challenge: Enhance Plot Aesthetics

Solution